1. Field of the Invention
The present invention relates to a power control unit for an electric vehicle, such as fuel cell electric vehicle, having a traction motor.
2. Description of the Related Arts
Due to discharge of no carbon dioxide gas, an electric vehicle has been focused which has batteries and a fuel cell and is driven by driving a motor for drive (hereinafter referred to as “traction motor”). The electric vehicle has a power control unit (hereinafter referred to as “PCU”) for electric vehicle in addition to the batteries and the traction motor. For example, referring to FIG. 1, in the case of a fuel cell electric vehicle 100 (hereinafter simply referred to as “vehicle”), an inverter (hereinafter simply referred to as “PDU”) to drive traction motor 104, a voltage control unit (hereinafter referred to as “VCU”), which controls the voltage between fuel cell 102 and capacitor 103 are accommodated within PCU 101.
In vehicle 101, fuel cell 102 and capacitor 103 are placed under the floor of the cabin, traction motor 104 is provided within a motor room, and PCU 101 is placed beneath traction motor 104, respectively (symbol W represents driving wheel and symbol S represents driving shaft, respectively). Between two of components, i.e., fuel cell 102, capacitor 103, traction motor 104, and PCU 101, are connected high voltage cables as shown by the block diagram of FIG. 2 in order to supply and receive electric power. Amongst high voltage cables, i.e., electric cables, a cable for connecting PCU 101 to fuel cell 2 is referred to as FC cable, a cable for connecting PCU 101 to capacitor 103 is referred to as CAPA cable, and a cable for connecting PCU 101 to traction motor 104 is referred to as MOT cable. It is noted that in order to the length of MOT cable is shortened whereby the loss of the electric power is minimized, PCU 101 is placed near traction motor 104.
The high voltage cables within the motor room have hitherto had a layout as shown in FIG. 11. FIG. 11A is a schematic view of PCU and traction motor disposed within the motor room viewing from a front side (of vehicle), FIG. 11B is a schematic view of PCU and traction motor disposed within the motor room viewing from a left side (of vehicle), and FIG. 11C is a schematic view of PCU, viewing from an upper side (in the situation where devices accommodated within PCU are omitted).
As can been seen from these figures, FC cable and CAPA cable are passed through a portion of a diaphragm (hereinafter referred to as “M/R diaphragm”) between traction motor 104 and motor room. The parts represented by symbol R is a reactor, which is an electric part functioning as a smoothing filter for noise reduction) accommodated within PCU 101.
If vehicle 100 is collided in a front or rear direction (i.e., head-on collision or rear-end collision), the motor room is sometimes crushed in the front or rear direction, causing deformation. This makes the gap between traction motor 104 and M/R diaphragm narrow, then making it difficult to detach FC cables and/or CAPA cables from PCU 101. Furthermore, FC cables and/or CAPA cables are caught into a space between traction motor 104 and M/R diaphragm, making it impossible to detach these cables. Such a situation then makes it impossible or difficult to perform maintenance with PCU 101 being detached. Consequently, a configuration is required in which the high voltage cables can be detached from the PCU 101 even if the motor room is deformed due to head-on and/or rear-end collision of vehicle. In the present situation, there takes a large gap between the traction motor 104 and M/R diaphragm. This, however, enlarges the wheelbase, improves the turning ability of vehicle 100 itself only with difficulty, and/or makes a cabin space small to thereby reducing livability. Also, in any case, depending upon the degree of deformation, FC cables and CAPA cables are caught in-between traction motor 104 and M/R diaphragm.
Since PCU 101 plays an important role in driving the vehicle, it should minimize the possibility of deforming box 101 against impact due to the collision to protect the functions of the devices accommodated within PCU 101 (box 110).
As for reactor R accommodated within PCU 101, upon supplying electric power, the surface of reactor R becomes high temperature due to Joule heat through the resistance of winding wires and Joule heat through the eddy current generated in the core. For this reason, electric parts and electronic parts are heated up through the radiant heat from reactor R, and have a fear of unstable actuation. If a space of the interior of PCU 101 (box 110) is enlarged in order to enhance ventilation so as to allow PCU 101 for effectively cooling, PCU 101 becomes large. However, it is not preferable from the functional viewpoint to dispose reactor R at a portion apart from PCU 101.